The main objective of the research being conducted in my laboratory is to understand at the molecular level the DNA: protein and protein: protein interactions that underlie the basic mechanism of DNA replication. The DNA replication proteins essential for DNA chain elongation and fork movement of the bacteriophage T4 have already been identified and purified to near homogeneity. When proteins are incubated in vitro, a replication apparatus can be constructed that mimics most of the characteristics of an in vivo DNA replication fork. Analysis of the partial reactions that comprise DNA chain elongation and fork movement with this protein apparatus are now underway in several other laboratories to elucidate the details of this mechanism. In the research being done in my laboratory we are utilizing this very successful model replication system and expanding it to include the T4 chromosome DNA initiation process whereby replication forks are generated at specific sites in vivo. The proteins that recognize a T4 origin and transform this DNA site to the DNA replicative "eye" form will be identified and purified. Maximum use is made of T4 genetics and previous studies that provide an excellent catalogue of available T4 DNA replication mutants from which to choose. The factors that provide the minimum necessary structure to get biologically correct DNA initiation at the T4 orgin(s) when combined with the T4 chain elongation-fork movement proteins already isolated should enable the entire DNA replication mechanism to be carried out in vitro, i.e., from DNA origin site recognition on the parental duplex DNA through progeny replication.